Zinc base alloys



Patented Jan. 8, 1946 ZINC BASE ALLOYS Edward S. Bunn, Rome, N. Y., assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a

corporation of Maryland No Drawing. Application March 13, 1943, Serial No. 479,111

8 Claims.

This application is a continuation-in-part of applicant's copending application Serial Number 421,809, filed December 5, 1941.

My invention, which will be best understood from the following description, relates to zinc base alloys, and has among its objects the production of mechanically workable zinc base alloys of improved characteristics.

It will be understood by those skilled in the art that commercially pure zinc when fabricated by hot or cold working has initially a moderately high tensile strength and a relatively high ductility. For example, hot rolled zinc commonly has a tensile strength of about 17,000 pounds per square inch and an elongation in 2 inches of about 45%.

Both hot and cold worked zinc however as it ages at room temperature gradually softens, and loses much 'of its tensile strength and most of its ductility. on account oi. a gradual coarsening of its crystalline structure, this phenomenon commonly called grain growth. Further, zinc cannot be hardened by cold working it on account of the heat generated by such working self annealing it.

The standard accepted test for determining the effect of age on zinc and its alloys is to subject them to an atmosphere of moist steam at 95 C. for 10 days. Hot rolled zinc having the tensile strength and ductility mentioned above will,

when so treated, have a tensile strength of about 11,000 pounds per square inch and a most meager elongation in 2 inches of about 2%. In other words, its tensile strength will be reduced by age as much as about 35% and its ductility as much as about 95%. Worked zinc therefore is clearly unstable at room temperatures in respect to tensile strength and ductility.

Applicant has found, that when suitable precautions are taken in making the alloys, the tensile strength of zinc may be markedly raised by alloying it with asmall amount of copper without seriously reducing its ductility, the resulting alloys, as compared to zinc, being markedly stable in respect to both tensile strength and ductility, particularly the latter. Amounts of copper up to 10% may be employed in the alloys when they are to be commercially hot rolled into sheets, and amounts up to 5% when they are to be commercially cold rolled into sheets.

The above described zinc-copper alloys form satisfactory substitutes for variou brasses, the

, copper.

be produced. Still further, their production and use as substitutes for brass act to release for other uses a supply of the strategic metal copper.

Applicant further has found that comparably the same results that are secured by adding small amounts of copper to zinc maybe secured by substituting for part of such copper a small amount of arsenic, thus enabling the same tensile strength to be secured with a lesser amount of Commonly, to secure the same tensile strength, the amount of arsenic will be much less than the amount of copper which it replaces,

thus enabling the same tensile strength in such most instances also effects an increase in the ductility of the alloy, causing it in that respect to approach near the high ductility of pure zinc, because of the lesser amount of alloying constituent present than if the same tensile strength were secured by adding copper alone. Thus, in most instances, the alloys in the main have improved characteristics over those in which the same tensile strength i secured by additions of copper alone. .Further, by substituting a small amount of arsenic for part of the copper, particularly when it is substituted for a larger amount of copper, a further saving of the expensive and strategic metal copper is effected when the resulting alloy'is substituted for brass.

The improved alloys may contain, approximately, 0.2 to 7.5% copper and 0.1 to 0.7% arsenic, provided the maximum amount of arsenic present does not exceed 0.25% when 7.5%

' copper is present, and, for amounts of copper less than 7.5%, does not exceed a value which varies approximately from 0.25 to 0.7% linearly and inversely with the percentage amount of copper within the range of copper specified, that is to say, as the amount of copper present increases from 0.2 to 7.5% the maximum permis-v sible amount of arsenic present decreases approximately linearly from 0.7% when 0.2% copper is present to 0.25% when 7.5% copper is present.

All the improved alloys may be readily commercially hot rolled, hot forged and hot extruded within a wide temperature range, and all of them are suiliciently fluid when in the molten state to be suitable for use for die casting purposes. If the amount of copper does not exceed about 4% the improved alloys have a very high degree of plasticity when cold, enabling them to be commercially cold rolled, cold spun, cold stamped and cold drawn with great facility. Further,

those with 1.5% and upward of copper do not self anneal during cold working, and hence may be hardened, or otherwise tempered, by cold working them. Extremely satisfactory alloys in all Further, securing the same tensile strength in this way in lowing table of the properties of the hot .rolled alloys. For convenience the corresponding binary zinc-copper alloy of the same tensile strength as each ternary zinc-copper-arsenic alloy is given in this table.

Elon- Tensile Elongation As Tensile gation strength in 2 inches strength in 2 after after steam inches steam test test Par Par Par cent cent P. r. i. cent P. a. 1. Per cent 0 0 17. 000 45 11, 000 2 2. l5 0 32. 000 45 27, 000 45 2. 0. 35 38, 000 40 31, 000 45 2. 5 0 38, 000 40 31, 000 40 2. 5 0. 2 40. 000 35 35, 000 35 3 0 40. 000 30 34. 000 28 3 0. 35 43. 000 30 37. 000 27 8. 75 0 43, 000 28 36, 000 25 Commonly additions of metallic constituents ofan additional alloy phase, either of which occurrences causes a gradual increase in the senic may be added to the molten copper by volume of the zinc and therefore a gradual increase in linear dimensions of articles fabricated In respect to the phenomena mentioned in the i I preceding paragraph it has been found that the addition of copper and arsenic within the ranges above mentioned produces ari alloy which also 1 has marked dimensional stability, the increase in linear dimensions of articles made of the alloy when subjected to the above mentioned steam test being approximately 15% of that which has heretofore commonly been deemed satisfactory for most commercial purposes.

If desired the slight dimensional instability of the alloy may be reduced or entirely eliminated by adding thereto small amounts of vanadium.

As little as 0.005% vanadium will have a marked effect in improving the dimensional stability, and amounts of vanadium in the order of 0.03% will vanadium'also improve the impact strength of the improved alloys and their stability in that respect.

For example, an alloy having 2.75% copper and 0.2% arsenic and a Charpy impact strength of 180 foot pounds per square inch before aging will have a Charpy impact strength of but about 64 foot pounds per square inch after being subjected to the above mentioned steam test. The addition of but 0.03% vanadium to this alloy, however, will raise this value to about 240 foot pounds per square inch for the unaged alloy with no deis formed separately from the molten zinc. when the zinc reaches the molten state'this molten mixture, which is of much higher temperature than the zinc, is poured into the latter, preferably slowly. Pouring the high temperature molten mixture into the relatively low temperature molten zinc causes a pronounced agitation and rise in temperature of the zinc, which act thoroughly to incorporate the mixture into the latter. Preierably, the molten. alloy thus formed is poured without delay into a mold to form a casting of suitable shape for the subsequent hot or cold working operations. To insure satisfactory results, deoxidized copper may be employed, or, if ordinary electrolytic copper is employed, a small amount of phosphorus or other deoxidant may be added, to the melt containing the copper, in sufiicient amount to deoxidize it, any residual phosphorus burning off. Also, to insure satisfactory results, the high temperature mixture likewise may be melted under a layer of charcoal, and preferably that mixture is poured into the moi-ten zinc and the resulting alloy poured into the mold not longer than'about 5 minutes after the zinc reaches the molten state. In making the high temperature mixture the bulk of the copper may be melted in a crucible, and the arthrowing into it small pieces of copper-arsenic alloy rich in arsenic. The vanadium, when employed, may be similarly added to the copper.

It will be understood that, within the scope of the appended claims, wide deviations may be made in the compositions of the alloys from those herein specifically mentioned.

I claim:

1. Workable alloys having, approximately, 0.2 to 7.5% copper, 0.1 to 0.7% arsenic, the balance being substantially zinc, the percentage amount of arsenic present not exceeding a value which varies approximately from 0.25 to 0.7% linearly and inversely with the percentage amount of copper present within the range of copper specified.

2. Cold workable alloys according to claim 1 having 0.2 to 4% copper, the variable maximum arsenic value being 0.45 to 0.7 for this range of copper.

3. Hot workable alloys according to claim 1 having 4 to 7.5% copper, the variable maximum arsenic value being 0.25 to'0.45% for this range of copper.

4. Cold workable alloys having, approximately, 1.5 to 3% copper and 0.1 to 0.5% arsenic, the balance being substantialy zinc.

5. Workable alloys according to claim 1 containing approximately 0.005 to 0.5% vanadium substituted for an equal amount of the zinc.

6. Cold workable alloys according to claim 1 having 0.2 to 4% copper and containing approximately 0.005 to 0.5% vanadium substituted for an equal amount of the zinc, the variable maximum arsenic value being 0.45 to 0.7% for this range of copper.-

"I. Hot workable alloys according to claim 1 having 4 to 7.5% copper and containing approx- -imately 0.005 to 0.5% vanadium substituted for crease at all in'that value as a result of subjecting the alloy to the steam test.

an equal amount of the zinc, the variable maximum arsenic value being 0.25 to 0.45% for this dium substituted for an equal amount of the zinc EDWARD S. BUNN. 

